What is asthma?

Asthma is a long-term disease of the airways of the lung. The airways become sensitive to triggers (allergens and irritants). With exposure to triggers, the following changes occur:

  • The lining of the airways becomes swollen and inflamed.
  • The muscles that surround the airways tighten.
  • More mucus is produced, leading to mucus plugs.

All of these factors cause the airways to narrow. This makes it hard for air to go in and out of the lungs.

What causes asthma?

The exact cause of asthma is unknown. It is believed to be partly inherited. The environment, infections, and chemicals released by the body are also involved.

Exercise causes symptoms in many people with asthma. Symptoms can occur during, or shortly after, exercise. In some people, stress or strong emotions can cause asthma symptoms.

All of the following may be asthma triggers:


Respiratory problem

  • Pollens (trees, grasses, and weeds)
  • Mold
  • Pets
  • Dust and dust mites
  • Cockroaches
  • Mice
  • Nasal allergies
  • Sinus infections
  • The flu
  • Viral infections, including the common cold



  • Strong odors perfumes, household cleaners, cooking fumes, paints, and varnishes
  • Chemicals (gases, fumes)
  • Air pollution
  • Changing weather conditions (temperature, barometric pressure, humidity, and strong winds)
  • Smoke (tobacco-inhaled or secondhand)
  • Aspirin
  • NSAIDs (nonsteroidal anti-inflammatory drugs) such as ibuprofen, indomethacin, naproxen

Other conditions

  • GERD (gastroesophageal reflux)
  • Sleep apnea
  • Overweight
  • Depression


  • Exercise, especially in cold weather
  • Strong emotions that go along with laughing or crying

Who is at risk for asthma?

It is most common in the following people:

  • Children and teens ages 5 to17
  • Those living in cities

Other factors include the following:

  • Personal or family history of asthma or allergies
  • Exposure to secondhand tobacco smoke
  • Children with a family history of asthma
  • Children who have allergies or atopic dermatitis
  • Children who have exposure to secondhand and tobacco smoke

What are the symptoms of asthma?

The symptoms of asthma include:

  • Trouble breathing or shortness of breath
  • Tightness in the chest
  • Wheezing or a whistling sound when breathing
  • Coughing
  • Breathing becomes harder and may hurt
  • Talking and sleeping may be difficult with severe symptoms

How is asthma diagnosed?

To diagnose asthma and rule out other lung disorders, health care providers rely on your medical history, physical exam, and other tests. An important test for the diagnosis and monitoring of asthma is spirometry.

A spirometer is a device that is used to determine how well the lungs are working. It measures the amount and speed of air exhaled.

Other tests may also be done to check for conditions such as allergies.